Test Prep for AP® Courses25

25.1 The Ray Aspect of Light

1. When light from a distant object reflects off of a concave mirror and comes to a focus some distance in front of the mirror, we model light as a _____ to explain and predict the behavior of light and the formation of an image.

  1. wave
  2. particle
  3. ray
  4. all of the above

2. Light of wavelength 500 nm is incident on a narrow slit of width 150 nm. Which model of light most accurately predicts the behavior of the light after it passes through the slit? Explain your answer.

25.2 The Law of Reflection

3. An object is 2 meters in front of a flat mirror. Ray 1 from the object travels in a direction toward the mirror and normal to the mirror’s surface. Ray 2 from the object travels at an angle of 5° from the direction of ray 1, and it also reflects off the mirror’s surface. At what distance behind the mirror do these two reflected rays appear to converge to form an image?

  1. 0.2 m
  2. 0.5 m
  3. 2 m
  4. 4 m

4. Two light rays originate from object A, at a distance of 50 cm in front of a flat mirror, diverging at an angle of 10°. Both of the rays strike a flat mirror and reflect. Two light rays originate from object B, at a distance of 50 cm in front of a convex mirror, diverging at an angle of 10°. Both of the rays strike the convex mirror and reflect. For which object do the reflected rays appear to converge behind the mirror closer to the surface of the mirror, thus forming a closer (larger) image? Explain with the help of a sketch or diagram.

25.3 The Law of Refraction

5. When light travels from air into water, which of the following statements is accurate?

  1. The wavelength decreases, and the speed decreases.
  2. The wavelength decreases, and the speed increases.
  3. The wavelength increases, and the speed decreases.
  4. The wavelength increases, and the speed increases.

6. When a light ray travels from air into glass, which of the following statements is accurate after the light enters the glass?

  1. The ray bends away from the normal, and the speed decreases.
  2. The ray bends away from the normal, and the speed increases.
  3. The ray bends toward the normal, and the speed increases.
  4. The ray bends toward the normal, and the speed decreases.

7.

Diagram shows two arrows running from point A to the top of a shaded box. Where they meet the shaded box, two new arrows emerge inside the box. These arrows meet at a point B inside the box.
Figure 25.57

Two different potential paths from point A to point B are shown. Point A is in the air, and point B is in water. For which of these paths (upper or lower) would light travel from point A to point B faster? Which of the paths more accurately represents how a light ray would travel from point A to point B? Explain.

8. Students in a lab group are given a plastic cube with a hollow cube-shaped space in the middle that fills about half the volume of the cube. The index of refraction of the plastic is known. The hollow space is filled with a gas, and the students are asked to collect the data needed to find the index of refraction of the gas. The students take the following set of measurements:

Angle of incidence of the light in the air above the plastic block: 30°

Angle of refraction of the beam as it enters the plastic from the air: 45°

Angle of refraction of the beam as it enters the plastic from the gas: 45°

The three measurements are shared with a second lab group. Can the second group determine a value for the index of refraction of the gas from only this data?

  1. Yes, because they have information about the beam in air and in the plastic above the gas.
  2. Yes, because they have information about the beam on both sides of the gas.
  3. No, because they need additional information to determine the angle of the beam in the gas.
  4. No, because they do not have multiple data points to analyze.

9. Students in a lab group are given a plastic cube with a hollow cube-shaped space in the middle that fills about half the volume of the cube. The index of refraction of the plastic is known. The hollow space is filled with a gas, and the students are asked to collect the data needed to find the index of refraction of the gas. What information would you need to collect, and how would you use this information in order to deduce the index of refraction of the gas in the cube?

10. Light travels through water and crosses a boundary at a non-normal angle into a different fluid with an unknown index of refraction. Which of the following is true about the path of the light after crossing the boundary?

  1. If the index of refraction of the fluid is higher than that of water, the light will speed up and turn toward the normal.
  2. If the index of refraction of the fluid is higher than that of water, the light will slow down and turn away from the normal.
  3. If the index of refraction of the fluid is lower than that of water, the light will speed up and turn away from the normal.
  4. If the index of refraction of the fluid is lower than that of water, the light will slow down and turn toward the normal.

11A laser is fired from a submarine beneath the surface of a lake (n = 1.33). The laser emerges from the lake into air with an angle of refraction of 67°. How fast is the light moving through the water? What is the angle of incidence of the laser light when it crosses the boundary between the lake and the air?

25.4 Total Internal Reflection

12. As light travels from air into water, what happens to the frequency of the light? Consider how the wavelength and speed of light change; then use the relationship between speed, wavelength, and frequency for a wave. What about light that is reflected off the surface of water? What happens to its wavelength, speed, and frequency?

25.6 Image Formation by Lenses

13. 

An object is 25 cm in front of a converging lens with a focal length of 25 cm. Where will the resulting image be located?

  1. 25 cm in front of the lens
  2. 25 cm behind the lens
  3. 50 cm behind the lens
  4. at infinity (either in front of or behind the lens)

14. A detective holds a magnifying glass 5.0 cm above an object he is studying, creating an upright image twice as large as the object. What is the focal length of the lens used for the magnifying glass?

15. A student wishes to predict the magnification of an image given the distance from the object to a converging lens with an unknown index of refraction. What data must the student collect in order to make such a prediction for any object distance?

  1. A specific object distance and the image distance associated with that object distance.
  2. A specific image distance and a determination of whether the image formed is upright or inverted.
  3. The diameter and index of refraction of the lens.
  4. The radius of curvature of each side of the lens.

16. Given a converging lens of unknown focal length and unknown index of refraction, explain what materials you would need and what procedure you would follow in order to experimentally determine the focal length of the lens.

25.7 Image Formation by Mirrors

17. A student is testing the properties of a mirror with an unknown radius of curvature. The student notices that no matter how far an object is placed from the mirror, the image seen in the mirror is always upright and smaller than the object. What can the student deduce about this mirror?

  1. The mirror is convex.
  2. The mirror is flat.
  3. The mirror is concave.
  4. More information is required to deduce the shape of the mirror.

18. A student notices a small printed sentence at the bottom of the driver’s side mirror on her car. It reads, “Objects in the mirror are closer than they appear.” Which type of mirror is this (convex, concave, or flat)? How could you confirm the shape of the mirror experimentally?

19. A mirror shows an upright image twice as large as the object when the object is 10 cm away from the mirror. What is the focal length of the mirror?

  1. -10 cm
  2. 10 cm
  3. 20 cm
  4. 40 cm

20.  mirror shows an inverted image that is equal in size to the object when the object is 20 cm away from the mirror. Describe the image that will be formed if this object is moved to a distance of 5 cm away from the mirror.